创建设备节点--手动方法

Android2.3及Linux2.6.29内核模拟器版本编译与调试

一、手动创建

1.驱动模块

test_driver.c

1. //#include <linux/devfs_fs_kernel.h>
2. #include <linux/module.h>
3. #include <linux/types.h>
4. #include <linux/uaccess.h>
5. #include <linux/miscdevice.h>
6. #include <linux/fs.h>
7. #include <linux/init.h>
8. #include <linux/platform_device.h>
9.  
10. #define TEST_MAJOR 240
11.  
12. //动态设备节点
13. //struct class *mymodule_class;
14. //结束
15. static int test_led_open(struct inode *inode, struct file *file)
16. {
17. printk("#########open######n");
18. return 0;
19. }
20.  
21.  
22. static int test_led_close(struct inode *inode, struct file *file)
23. {
24. printk("#########release######n");
25. return 0;
26. }
27.  
28.  
29. static int test_led_read(struct file *filp, char __user *buff, size_t count, loff_t *offp)
30. {
31. printk("#########read######n");
32. return count;
33. }
34.  
35. static int test_led_write (struct file *filp, const char __user *buf, size_t count,loff_t *f_pos)
36. {
37. printk("#########write######n");
38. return count;
39. }
40.  
41.  
42. static struct file_operations led_fops = {
43. .owner = THIS_MODULE,
44. .open = test_led_open,
45. .release = test_led_close,
46. .read = test_led_read,
47. .write = test_led_write,
48. };
49.  
50. static int __init test_drv_init(void)
51. {
52. int rc;
53. printk("test_driver devn");
54. //注册设备
55. rc = register_chrdev(TEST_MAJOR,"test_dev",&led_fops);
56. if (rc <0){
57. printk ("register %s char dev errorn","led");
58. goto out_chrdev;
59. }
60. //devfs文件系统创建
61. /*
62. devfs_mk_cdev( MKDEV(TEST_MAJOR, 0),
63. S_IFCHR | S_IRUSR | S_IWUSR | S_IRGRP, "test_dev");
64. */
65. //结束
66. //实现动态创建
67. //mymodule_class = class_create(THIS_MODULE, "test_dev");//在/sys/class/下创建“test_dev”目录
68. //device_create(mymodule_class, NULL, MKDEV(TEST_MAJOR, 0), NULL, "tankai_dev"); //在/dev/下创建“tankai_dev”文件
69. //结束
70. printk ("ok!n");
71. return 0;
72.  
73.  
74. out_chrdev:
75. unregister_chrdev(TEST_MAJOR, "mymodule");
76. }
77.  
78. static void __exit test_drv_exit(void)
79. { //动态设备节点
80. //device_destroy(mymodule_class, MKDEV(TEST_MAJOR, 0));
81. //class_destroy(mymodule_class);
82. //结束
83. unregister_chrdev(TEST_MAJOR, "test_dev");
84. }
85.  
86. module_init(test_drv_init);
87. module_exit(test_drv_exit);
88.  
89. MODULE_AUTHOR("tank");
90. MODULE_LICENSE("GPL");

Makefile

1. obj-m := test_driver.o
2. PWD := $(shell pwd)
3. #KERNELDIR := /usr/src/linux-headers-3.0.0-26-generic/
4. KERNELDIR := /home/android2.3/android2.3_kernel/
5. default:
6. $(MAKE) -C $(KERNELDIR) M=$(PWD) modules
7. # cp -rf mini.ko ../module/
8. # cp -rf lddbus.ko ../module/
9. clean:
10. rm *.mod.c *.o *.ko *.bak modules.* Module.*

2.Android模拟器没有mknod命令，我们实现它

mknod.c

1. #include <stdio.h>
2. #include <fcntl.h>
3. #define S_IFCHR 0020000
4.  
5. int main(int argc,char *argv[])
6. {
7. if(argc != 3){
8. printf("error:Two canshun");
9. return -1;
10. }
11. char *devname = argv[1];
12. printf("devname is %sn",devname);
13. int devnum = -1;
14. sscanf(argv[2],"%d",&devnum);
15. printf("devnum is %dn",devnum);
16. if(mknod(devname,S_IFCHR|0666,makedev(devnum,0))!=0)
17. perror("mknod");
18. return 0;
19. }

Android.mk

1. LOCAL_PATH:= $(call my-dir)
2. include $(CLEAR_VARS)
3.  
4. LOCAL_SRC_FILES:=
5. mknod.c
6.  
7. LOCAL_SHARED_LIBRARIES :=
8. libutils
9.  
10. LOCAL_MODULE:= mknod
11.  
12. LOCAL_MODULE_TAGS := optional
13.  
14. include $(BUILD_EXECUTABLE)

查看：cat /proc/devices

结果：

1. Character devices:
2. 1 mem
3. 4 /dev/vc/0
4. 4 tty
5. 5 /dev/tty
6. 5 /dev/console
7. 5 /dev/ptmx
8. 7 vcs
9. 10 misc
10. 13 input
11. 14 sound
12. 29 fb
13. 90 mtd
14. 116 alsa
15. 128 ptm
16. 136 pts
17. 240 test_dev
18. 253 ttyS
19. 254 rtc
20.  
21. Block devices:
22. 1 ramdisk
23. 259 blkext
24. 7 loop
25. 31 mtdblock
26. 43 nbd
27. 179 mmc
28. 254 device-mapper

执行：./mknod /dev/tankai_dev 240

//这里只需要给出主设备号，主设备号相同的设备使用同一驱动程序；只是加入次设备号后可以实现一个驱动，多个设备使用的情况。这个目前我们的驱动中没有实现；因此，次设备号可以随便。

ll /dev/tankai_dev

结果：

1. crw-rw-rw- root root 240, 0 2013-10-16 09:54 tankai_dev

3.测试用例

testdriver.c

1. #include <fcntl.h>
2. #include <stdlib.h>
3. #include <sys/mman.h>
4. #include <errno.h>
5. #include <sys/types.h>
6. #include <sys/stat.h>
7. #include <string.h>
8.  
9. int main(){
10. int fd = open("/dev/tankai_dev",O_RDWR,0);
11. if(fd < 0) perror("testdriver");
12. printf("TK------->>>fd is %dn",fd);
13. char buf[20];
14. int result = read(fd,&buf,3);
15. printf("TK------->>>readresult is %d,buf is %sn",result,buf);
16. strcpy(buf,"123");
17. result = write(fd,&buf,3);
18. printf("TK------->>>writeresult is %d,buf is %sn",result,buf);
19. close(fd);
20. return 0;
21. }

Android.mk

1. LOCAL_PATH:= $(call my-dir)
2. include $(CLEAR_VARS)
3.  
4. LOCAL_SRC_FILES:=
5. testdriver.c
6.  
7. LOCAL_SHARED_LIBRARIES :=
8. libutils
9.  
10. LOCAL_MODULE:= testdriver
11.  
12. LOCAL_MODULE_TAGS := optional
13.  
14. include $(BUILD_EXECUTABLE)

二、自动创建

放通驱动中“创建”和“结束”部分代码；就不需要在执行mknod命令，设备节点会被创建，见：《Linux设备节点创建》内核kobject上报uevent过滤规则 及 《Linux设备节点创建》用户空间ueventd创建设备节点规则。